Race-specific associations of myeloperoxidase with atherosclerosis in a population-based sample: The Dallas Heart Study

Objective: Myeloperoxidase (MPO) is a leukocyte-derived enzyme that appears to be directly involved in atherosclerosis development. We evaluated the association of circulating MPO with coronary and aortic atherosclerosis in a large, multiethnic population. Methods and results: Plasma levels of MPO were measured in 3294 subjects participating in the Dallas Heart Study, a probability-based population sample. Coronary artery calcification (CAC) was measured by EBCT, and abdominal aorta plaque prevalence (AP) and burden (APB), as well as abdominal aorta wall thickness (AWT) were determined by MRI. Associations between MPO and atherosclerosis phenotypes were assessed in multivariable analyses adjusting for traditional atherosclerosis risk factors. MPO levels in the 4th compared with 1st quartile independently associated with prevalent AP (OR 1.41, 95% CI 1.08-1.84), APB (beta coefficient 0.23, p=0.02), and AWT (beta coefficient 0.04, p=0.03), but not with prevalent CAC (OR 0.84, 95% CI 0.61-1.17). MPO remained associated with aortic atherosclerosis phenotypes but not coronary calcification after adjustment for other inflammatory biomarkers. A significant interaction was observed between race/ethnicity, MPO and AP (p _interaction=0.038), such that MPO levels in the 4th vs 1st quartile associated with prevalent AP in African Americans, (OR 1.81, 95% CI 1.23-2.65) but not in White or Hispanic participants (OR 0.99, 95% CI 0.68-1.44). Conclusion: Higher levels of MPO associated with aortic but not coronary atherosclerosis, with significant associations limited to African American participants. These findings suggest that MPO might be a novel risk factor contributing to racial disparities in peripheral vascular disease.